Electrocoating composition of a polyamine self-condensed epoxy adduct and coatings produced thereby

Abstract

The invention relates to a novel electrocoating composition for metallic substrates that exhibits "thick-build" protective properties at "medium-build" thicknesses. It is composed of a self-addition epoxy resin-polyamine adduct, a blocked isocyanate cross-linker, a polyglycol-polyamine grind resin, a plasticizer, an anti-cratering agent and pigments.

We claim: 
     
       1. A coating composition comprising: a principal resin comprising a self-addition epoxide resin-polyamine adduct with pendant alkylphenoxy groups;   a cross-linker comprising a blocked polyisocyanate compound;   a grind resin comprising the reaction product of an aromatic diepoxide, a bis (aromatic alcohol), a polyglycolamine, a diamine and an alkaryl monoepoxide;   a plasticizer; and   pigments selected from a group consisting of inorganic, organometallic and organic compounds.   
     
     
       2. A composition according to claim 1, further comprising a defoamer, neutralizing acids and solvents. 
     
     
       3. A composition according to claim 1, further comprising an anti-cratering agent selected from polyacrylate resins, polyether resins, polyester resins, and silicone resins 
     
     
       4. A composition according to claim 3 wherein said anti-cratering agent is a polyacrylate resin having alkyl, aromatic, and dialkylamino pendant groups. 
     
     
       5. A composition according to claim 1 wherein said crosslinker is a toluene diisocyanate compound, a blocked isocyanurate of a hexane diisocyanate compound or mixtures thereof. 
     
     
       6. A composition according to claim 1 wherein said plasticizer is a poly(alkylene oxide) alcohol compound. 
     
     
       7. A composition according to claim 1, wherein the principal resin is the reaction product of a self-addition epoxide resin and a mixture of amines selected from the group consisting of amino alcohols and alkyldiamines, the equivalent ratio of amine mixture to adduct being from about 0.75 to 1 amine equivalent per epoxide group; the self-addition epoxide resin being the reaction product of an aromatic or alkylaromatic diepoxide having a molecular weight of from about 350 to 1500 and a phenol of the formula RC 6  H 4  OH wherein R is hydrogen or an alkyl group of from 1 to 18 carbons, and the equivalent ratio of diepoxide to alkyl phenol being about 3 to 8 epoxy groups per phenol group.   
     
     
       8. A composition according to claim 7 wherein the equivalent ratio of diepoxide to alkylphenol is 3.5 to 4.5 epoxy groups per phenol group. 
     
     
       9. A composition according to claim 8, wherein the diepoxide is formed by reacting bisphenol A and a diglycidyl ether wherein the diglycidyl ether has a molecular weight of from about 300 to about 800. 
     
     
       10. A composition according to claim 7, wherein the adduct is formed from bisphenol A, glycidyl chloride and alkyl glycidyl ether of from about 4 to 12 carbons. 
     
     
       11. A composition according to claim 1, wherein the cross-linker is the reaction product of trimethylolpropane, toluene diisocyanate and an alkyl alcohol of from 4 to 12 carbons. 
     
     
       12. A composition according to claim 1, wherein the cross-linker is the reaction product of the isocyanurate of hexane-1,6-diisocyanate and a secondary amine. 
     
     
       13. A composition according to claim 12, wherein the secondary amine has from 3 to 6 carbons in each alkyl group. 
     
     
       14. A composition according to claim 1, wherein the grind resin is a reaction product of bisphenol A diglycidyl ether, bisphenol A, nonylphenyl glycidyl ether, N,N-dimethyl propylene diamine and 9-amino-3,6-dioxanonan-1-ol. 
     
     
       15. A composition according to claim 1, wherein the plasticizer is nonylphenoxypolypropoxy alcohol or cresyloxypolypropoxy alcohol. 
     
     
       16. A composition according to claim 1, wherein the anti-cratering agent is a polymer of C 1  -C 6  alkyl acrylate, styrene, C 1  -C 6  hydroxyalkyl acrylate and dimethylaminoethyl acrylate. 
     
     
       17. A composition according to claim 1, wherein the weight percent ranges of ingredients relative to total weight of nonvolatile solids are about 30% to 55% of principal resin, about 15% to 30% of cross-linker, up to about 20% of grind resin, about 3% to 12% plasticizer, up to 35% pigments and up to about 3% anti-cratering agent. 
     
     
       18. A composition according to claim 17, wherein the weight percentages are about 40% principal resin, about 22% cross-linker, about 7% grind resin, about 5.5% plasticizer, about 25% pigments, and about 0.5% anti-cratering agent. 
     
     
       19. A coating composition comprising: about 30% to 55% of a principal resin formed by adducting a mixture of an amino alcohol of 4 to 8 carbons and primary/tertiary diamine with the self-condensate of an alkyl phenol of the formula RC 6  H 4  OH, R being hydrogen or an alkyl of 1 to 18 carbons, and bisphenol A-liquified-bisphenol A diglycidyl ether having a molecular weight of about 350 to 1500; about 15% to 30% of a blocked isocyanate cross-linker formed from trimethylol propane, toluene diisocyante and alkyl alcohol of 4 to 12 carbons, or from the isocyanurate of hexane-1,6-diisocyanate and secondary amine having from 3 to 6 carbons in each alkyl group, or a mixture thereof;   up to about 20% of a grind resin formed from bisphenol A diglycidyl ether, an aromatic diol, 9-amino-3,6-dioxanonan-1-ol, N,N-dialkyl alkylenediamine of 4 to 12 carbons and nonylphenolmonoglycidyl ether;   about 3% to 12% of a plasticizer comprising nonylphenoxypolypropoxy alcohol or cresyloxypolypropoxy alcohol; and   up to about 35% pigments comprising inorganic, organometallic, or organic compounds or mixtures thereof;   the percentage being in weight relative to the total weight of the composition.   
     
     
       20. A composition according to claim 19 further comprising up to about 3% of an anti-cratering agent comprising a polymer of alkyl acrylate, styrene, hydroxyalkyl acrylate and dimethylaminoethyl acrylate. 
     
     
       21. A coating composition comprising: about 40% of a principal resin formed by adducting a mixture of diethanolamine and N,N-dimethylpropylene diamine with the self-condensate of nonylphenol and the diepoxide bisphenol A-liquified-bisphenol A diglycidyl ether having a molecular weight of 350 to 1500;   about 22% of a blocked isocyanate cross-linker formed from trimethylolpropane, toluene diisocyanate and 3-oxahexan-1-ol;   about 7% of a grind resin formed from bisphenol A diglycidyl ether, bisphenol A, nonylphenylmonoglycidyl ether, 9-amino-3,6-dioxanonan-1-ol and N,N-dimethylpropylene diamine;   about 5.5% of a plasticizer selected from nonylphenoxypolypropoxyethanol and cresylphenoxypolypropoxyethanol;   about 0.5% of an anti-cratering agent comprising a polymer of butyl acrylate, 2-hydroxyethyl acrylate, dimethylaminoethyl acrylate and styrene; and   about 25% pigments comprising inorganic, organic compounds mixtures thereof.   
     
     
       22. A coating composition according to claim 19, 20 or 21 wherein the equivalent ratio of amine mixture to self-addition epoxy resin is from about 0.75 to about 1 amine equivalent per epoxide group. 
     
     
       23. A coating composition according to claim 19, 20 or 21 wherein the equivalent ratio of diepoxide to alkylphenol is 3:1 to 8:1 epoxy to phenoxy groups. 
     
     
       24. A coating composition according to claims 19, 20 or 21 wherein the equivalent ratio of diepoxide to alkylphenol is 3.5:1 to 4.5:1 epoxy to phenoxy groups. 
     
     
       25. A coating bath comprising a mixture of about 20 to 30 weight percent of the composition of any one of claims 1 through 21, and a remaining weight percent of defoaming agents and an acidic, aqueous medium of pH about 4.5 to 7. 
     
     
       26. An article electrocoated with a composition according to any one of the claims 1 through 21.